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Hashemi Eye Care - Neuroscience Institute and Research Center

Panretinal Photocoagulation (PRP)

Laser treatment for proliferative diabetic retinopathy and other conditions with abnormal blood vessel growth. Learn how it prevents blindness.

7 min read

Panretinal photocoagulation (PRP), also called scatter laser treatment, is a laser procedure used to treat proliferative diabetic retinopathy (PDR), certain retinal vein occlusions, and other conditions where abnormal blood vessels grow in the eye. By treating the peripheral retina with laser, PRP reduces the stimulus for abnormal vessel growth and helps prevent severe vision loss.

Key Takeaways

  • Laser treatment to peripheral retina—typically 1,000-2,000 spots
  • Prevents vision loss from proliferative diabetic retinopathy
  • Reduces neovascularization (abnormal blood vessel growth)
  • May be done in multiple sessions
  • Side effects: reduced peripheral and night vision, usually well tolerated
  • Proven effective—reduces severe vision loss by ~50%

How PRP Works

The Problem It Addresses

In conditions like PDR:

  • The retina becomes ischemic (oxygen-starved)
  • Ischemic retina releases VEGF and other growth factors
  • These factors stimulate new blood vessel growth (neovascularization)
  • New vessels are fragile and cause bleeding, scarring, retinal detachment
  • This leads to severe vision loss

The Solution

PRP treats the ischemic peripheral retina:

  • Laser destroys oxygen-hungry retinal cells
  • Reduces overall retinal oxygen demand
  • Decreases production of growth factors (VEGF)
  • New blood vessels regress or don't form
  • Preserves central vision by sacrificing some peripheral vision

The Trade-off

PRP represents a calculated trade-off:

By treating (and partially destroying) the peripheral retina, we reduce the stimulus for devastating complications that would cause complete vision loss. Some peripheral and night vision may be lost, but central vision is preserved.

Indications

Primary Indications

Proliferative Diabetic Retinopathy:

  • New vessels on the disc (NVD)
  • New vessels elsewhere (NVE)
  • Especially with vitreous hemorrhage
  • High-risk characteristics

Ischemic Retinal Vein Occlusion:

Other Conditions:

  • Neovascular glaucoma (or risk thereof)
  • Sickle cell retinopathy with neovascularization
  • Ocular ischemic syndrome
  • Radiation retinopathy

The Procedure

Before Treatment

  • Pupils are dilated
  • Anesthetic drops applied
  • Contact lens placed on eye for focusing
  • May receive injection of anesthetic around eye for comfort

During Treatment

  1. You sit at the laser machine (similar to slit lamp exam)
  2. Contact lens is placed on your eye
  3. Laser is applied in bursts to the peripheral retina
  4. You'll see flashes of light
  5. Typically 300-500 spots per session
  6. Usually takes 15-30 minutes

Treatment Sessions

  • Traditional approach: 2-4 sessions over 2-4 weeks
  • Single session: increasingly common with modern lasers
  • Total: 1,200-2,000 laser spots typically needed

What You'll Experience

  • Bright flashes of light during laser
  • May feel some discomfort (described as stinging or aching)
  • Some patients feel a "pulling" sensation
  • Discomfort usually manageable
  • Pain medication or additional anesthesia available if needed

After Treatment

Immediately After

  • Vision will be blurry (from dilation, laser effect)
  • May have some discomfort
  • Pupils remain dilated for several hours
  • Someone should drive you home

First Few Days

  • Vision may be reduced temporarily
  • Some patients notice peripheral vision changes
  • Night vision may be affected
  • Usually improves over following weeks

Follow-Up

  • Return visit in 1-2 weeks to assess response
  • May need additional laser sessions
  • Continued monitoring for new vessels
  • May need anti-VEGF injections as well

Side Effects

Expected Effects

Common side effects that are expected:

  • Reduced peripheral (side) vision—varies by individual
  • Reduced night vision—difficulty adapting to dark
  • Reduced color vision (mild)—usually not noticeable
  • Temporary blur—resolves over days to weeks

These are the trade-off for preventing blindness from proliferative disease.

Possible Complications

  • Accidental laser to macula (rare with experienced surgeon)
  • Worsening macular edema (may need treatment)
  • Choroidal effusion or detachment (usually resolves)
  • Vitreous hemorrhage (may occur even with treatment)
  • Decreased accommodation (focusing ability)
  • Visual field constriction significant enough to affect driving (uncommon)

Effectiveness

Clinical Evidence

Landmark studies (Diabetic Retinopathy Study) showed:

  • PRP reduces severe vision loss by ~50%
  • Benefit persists long-term
  • Earlier treatment generally better

Modern Context

Today, PRP is often combined with:

  • Anti-VEGF injections—rapid effect on new vessels
  • Injections given, then PRP consolidates the response
  • May reduce total amount of laser needed

PRP vs. Anti-VEGF Injections

Feature PRP Anti-VEGF
Effect duration Long-lasting/permanent Temporary (needs repeat injections)
Speed of effect Slower (weeks) Rapid (days)
Side effects Peripheral vision loss Injection risks
Cost over time Lower (fewer treatments) Higher (ongoing injections)
Office visits Fewer after completion More frequent

Current practice often combines both approaches.

Living with PRP

What to Expect Long-Term

  • Some peripheral vision loss is typical
  • Most people adapt well
  • Central vision (for reading, recognizing faces) is preserved
  • Night driving may be challenging
  • May need to turn head more to see peripherally

Driving Considerations

  • Most patients can continue driving
  • May have difficulty meeting legal visual field requirements in some cases
  • Night driving may be affected
  • Discuss with your doctor if concerned

Follow-Up Care

  • Continued diabetic retinopathy monitoring
  • May need additional PRP if new vessels recur
  • Continued systemic management (blood sugar, blood pressure)
  • Annual dilated exams minimum

Frequently Asked Questions

Will PRP cure my diabetic retinopathy?

PRP doesn't cure diabetic retinopathy but prevents the worst complications (blindness from proliferative disease). You'll still have diabetic eye disease and need ongoing monitoring and blood sugar control.

Will I go blind from the laser?

No. PRP is designed to prevent blindness. While it does reduce some peripheral and night vision, it protects your central vision from the devastating effects of untreated proliferative disease.

How many laser sessions will I need?

This varies. Traditionally, 2-4 sessions were standard. With modern lasers, single-session PRP is increasingly possible. Your doctor will assess your response and determine if additional treatment is needed.

Can I drive after PRP?

Not immediately after the procedure (you'll be dilated and vision blurry). Once recovered, most patients can drive, though some experience peripheral vision changes that could affect driving. Discuss with your doctor.

Why do I also need injections?

Anti-VEGF injections work quickly to reduce new vessels, while PRP provides lasting treatment. Combining them often gives better results than either alone. Injections address macular edema; PRP addresses proliferative disease.

Is PRP painful?

Many patients describe it as uncomfortable rather than painful. You may feel stinging, aching, or pressure. Anesthetic drops are used, and additional anesthesia can be given if needed. The discomfort is temporary.

Can the laser damage my central vision?

In experienced hands, this is extremely rare. The laser is deliberately aimed at the peripheral retina, away from the macula. The contact lens used helps ensure accurate targeting.

What happens if I don't get PRP?

Untreated proliferative diabetic retinopathy has a high risk of severe vision loss. Abnormal vessels can bleed (vitreous hemorrhage), cause retinal detachment, or lead to neovascular glaucoma. PRP significantly reduces these risks.

References

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